1. Field of the Invention
The invention relates in general to a system and a method for projection correction, and more particularly to a system and a method for real-time projection correction.
2. Description of the Related Art
Along with the development of projector in past years, digital projectors have already been one of indispensable multimedia tools, and are often applied to various use such as the family video and music, the digital teaching, the meeting report, and so on. Because of included angle problems, traditional projectors usually project original images on a projection screen with the trapezoid distortion phenomenon, thus generating distorted projection images. Therefore, the projectors generally provide the trapezoid correction function.
To improve the above trapezoid distortion phenomenon, an image processing system is disclosed in U.S. Pat. No. 7,470,029. In this image processing system, a projector projects an entirely-white testing image in advance to obtain a set of corner coordinates corresponding to the entirely-white testing image, and then projects an original image to obtain another set of corner coordinates corresponding to the original image. The image processing system compares the two sets of corner coordinates to obtain a distance between the projector and a projection screen, and then calculates the coordinates in the three-dimensional space to obtain a posture of the projector and accordingly corrects the projection image. However, the above image processing system is not suitable for real-time correction because of the calculation of the coordinates of multiple points and the complicated coordinate transformation.
Moreover, a method for correcting distorted images is disclosed in U.S. Pat. No. 6,753,907. The method utilizes projects and cameras disposed at different positions to capture the projection image and find out a transformation matrix between a projection image and a capture image, and find a transformation matrix between a projection screen and the capture image, and then obtains a transformation matrix between the projection image and the projection screen according to the above two transformation matrices. Said method for correcting distorted images corrects the projection image by utilizing the transformation matrix between the projection image and the projection screen. However, the above method for correcting distorted images is still not suitable for real-time correction because of the complicated calculation of these coordinate transformation matrices.
However, along with a high development of mobile devices, mobile-type hand-held micro projectors or micro projectors integrated in mobile devices have gradually broad applications. Because the micro projectors are not fixed, even shaking at any time, it has to perform a real-time trapezoid correction function of projection images in accordance with postures of the micro projectors. Therefore, the time-consuming image correction method with complicated calculation processes and heavy computation load is not suitable for the micro projectors.